Such packaging machines are not only known in practice, but they are also known e.g. from DE 10 2007 013 698 A1. They are based on the finding that packed products can have a particularly long shelf life when a specific concentration of a specific gas (or of a plurality of gases), which deviates from the ambient air, exists in the package. It follows that, before the package filled with the product in question is closed in a gastight manner, this gas or gas mixture is introduced in the package in the ideal concentration, after the ambient air previously contained in the package has been, or is being evacuated from the package.
For obtaining the longest possible shelf life of the products, it is necessary that the gas or gas mixture concentration neither falls below nor exceeds the ideal concentration range of the gas or gas mixture. It follows that the gas mixture introduced and contained in the packages and the leak tightness of the chamber will be have to be measured regularly. For this purpose, conventional packaging machines were equipped with a gas concentration sensor which, via a measurement input, took a gas sample from the packaging machine chamber used for gas flushing, and evaluated this sample. The measurement value represented the reference value for all the packages contained in the chamber.
This conventional measurement principle has various drawbacks. On the one hand, there is a delay in the measurement, since the gas sample must first be transferred to the gas sensor via the measurement gas line. On the other hand, the measurement values will be flawed with inaccuracies, when the measurement line of the gas sensor has not been fully flushed with the filling gas of the new cycle prior to carrying out a new measurement. Moreover, there is the risk that, together with the gas sample, residues of liquids or dirt arrive at the gas sensor, which may not only corrupt the measurement values but also damage the gas sensor permanently.